Posted
by
michael
on Tuesday August 24, 2004 @06:02PM
from the horseshoes-and-hand-grenades dept.

tricaric writes "Another asteroid passed, last March 31st, close to the Earth. This time it was only about 2 Earth radii from the Earth. The observation have been published only a few days ago, because 'Although the observed arc is only 44 minutes, the orbit is quite determinate and, given the exceptional nature of this close approach, the object is now receiving a designation.' Check out the ORSAanimation!"

But the fun now isn't in shouting "WE'RE ALL DOOMED, THE END IS NIGH!!", but it's guessing the cause of our end. Asteroids, Aliens, Super Volcanos, Landsliding islands, Runaway Computer Viruses, Bad Holywood Movies, Global Warming, POTUS, run over by a bus, or whatever else tickles your fancy.

If you don't believe me, try to find a copy of "The Guns of El Chupacabra." "Gigli" seems like an Academy Award winner in comparison.

I could only stand it for about half an hour, and that even though the executive producer is a friend of mine and gave me a numbered promotional copy. Some of the music is actually pretty good, but they should have just recorded the bands and fired everyone else.

Yeah, but it would've made many satellite operators nervous to not have a good orbit determination. A collision in geo makes a mess and takes away much of that real estate for quite some time. Orbital traffic management for both known and 'alien' bodies such as this asteroid is a growing concern among those in the space operations business.

Wouldn't it be prudent to put in the story text that the object is estimated to be only 6 meters in diameter?

The article states that an object that size would burn up harmlessly in the atmosphere. I'm not sure if that's correct or not... a 6 meter hunk of material would probably rain at least SOME material down on the ground, but I don't know if it would make a crater.

The point is that we didn't just narrowly escape certain doom... it was a small rock.

A six-meter rock, if it doesn't break up in the atmosphere, will make a respectable crater -- maybe even knock down a few buildings. If it does break up, the fragments won't be big enough to leave craters, but can still hit hard enough to damage buildings or kill people.

A six-meter rock, if it doesn't break up in the atmosphere, will make a respectable crater -- maybe even knock down a few buildings.

I'm not sure what the relative velocity of the object compared to the earth's was, but if we estimate 20 km/s and a mass of 300 tons, then the kinetic energy of this object is about 6e13 J. That is about 15 kilotons of TNT worth of kinetic energy that you have to get rid of during the 1-2 seconds it takes to cross the atmosphere. The Hiroshima bomb was about 20 kilotons. I do

If it's a cabonaceous chondrite (the most common type) it would almost certainly burn up and/or explode high in the atmosphere with little material reaching the surface. If its solid nickle iron it might very well reach the surface intact and make quite a hole.

It's roughly two really small cars or one biggun. A Volvo 240 (the new yardstick for measuring asteroids, since I happen to have one handy) is just over 5 meters long. So if it helps, think of it as a large Volvo hurtling towards us from outer space at thousands of kilometers per hour (I'll save the detailed kph comparisons for later, but a standard Volvo 240 normally tops out at between 160 and 210kph depending on the engine).

Calculating how many Volvos there are in one Rhode Island is left as an exercise for the reader.

Orbital velocities are usually of some tens of kilometers per second, which easily makes for hundreds of thousands mph. But such a small object would be slowed down by the atmosphere, and by the time it would hit the ground (assuming it would arrive intact at all) it wouldn't be much faster than terminal velocity - say 200 or 300 mph. Even on a populated area, it would do relatively little damage.

According to Earth Speeds [enchantedlearning.com], the Earth goes around the Sun at approximately 18.5 miles/sec, or 30 km/sec. In six hours the Earth will move 400,000 miles or 650,000 km around the sun. The radius of the Earth is roughly 4,000 miles or 6,500 km. So in six hours the Earth moves about 100 times its radius.

The original observations posted to the Harvard project site were pulled. I'm guessing they fearedcontroversies such as have occurred in the recent past when estimates were revised to preclude impact.I think hiding the data is irresponsible in all cases, and it makes me distrust astronomers across the board.

What's your point? I was talking about the slashdot headline. In fact the entire/. story failed to mention the word "astrometrically." Just proving that once again slashdot editors and story submitters don't RTFA.

Right below the article there's small note explainning why it was a remarkable observation:

"is by far the closest ever observed astrometrically." The distinction is important, because the title of "closest ever observed" probably belongs to the well documented Great Daylight Fireball of 1972. On August 10th many witnesses, including a meteor expert, saw and photographed an object of about 2004 FU162's size fly through Earth's atmosphere, traveling from south to north along the Rocky Mountains of the U.S.

Consider what might happen if this particular rock did hit us. 6 meters isn't enough to wipe out a city and it's unlikely that it would have hit in a populated area. Assuming that it didn't kill or hurt anyone, it might have been a good thing if it hit the ground.

Why? Because a big, fat, headline making impact (or splash) would really catch everyone's attention. A miss just catches our (the nreds') interest for a bit. If people perceive that there is an actual threat, perhaps space exploration and planetary defense will be taken seriously for a change.

My eyes kept getting wider and wider! Granted, I wasn't aware of the object's size when I saw it, but still!

In case you miss it, those little circles around Earth that you can't even read when the animation begins are the orbits of geosynchronous satellites, such that provide GPS, weather images, and satellite TV!

If you want to call that an asteroid, then this [http] is also an asteroid? This was a meteor that passed right through Earth's atmosphere in 1976, with a perehelion of 58,000 metres.

Although, I think the point here is that this is the closest observed astronomically. It's like seeing the meteor before it hits the atmosphere, I guess. Anyway, the astronomers are all in a tizzy over it, so that must be a good thing.